Fuse



July 16, 1940. T. BIRKENMAIER FUSE Filed March 24, 1939 2 Sheets-Sheet lFIG. l.

July 15, 1940- T. BIRKENMAIER 2,208,407

FUSE

Filed March 24, 1939 2 Sheets-Sheet 2 19% Flc/5,6 Flos.

Patented July 16, 1940 PATENT OFFICE FUSE Theodore Birkenmaier, St.Louis, Mo., assigner to l W. N. Matthews Corporation, St. Louis, Mo., a

' corporation of Missouri Application March 24, 1939, Serial No. 263,857

4 Claims.

This invention relates to fuses, and with regard to certain morespecific features, to closed type fuse switches.

This invention is an improvement upon the construction shown in myVUnited States Patent 2,176,045, dated October 17, 1939 for Fuse.

Among the several objects of the invention may be noted the provision ofa closed type of fuse switch of the class shown in said application 10in which a greater visible indication and electrical clearance isprovided in its blown condition; and the provision of a switch of theclass described in which a more complete enclosure is provided underunblown conditions. Other ob out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts whichdescribed, and the scope of the application of which will be indicatedin the following claims.

In the accompanying drawings, in which is illustrated one of variouspossible embodiments of the invention,

Fig. 1 is a vertical section through the apparatus which is shown inclosed, circuit-oonnectingposition;

Fig. 2 is a 'horizontal section taken on line 2--2 of Fig. 1;

Fig, 3 is a horizontal section takenl on line 3-3 of Fig.\1;'

Fig, 4 is a bottom plan view of Fig. 1;

Fig. 5 is a view similar to Fig. 1 showing an intermediate blowncondition, certain parts being shown in elevation;

Fig. 6 is a view similar to Fig. 1 showing a final blown condition, moreparts being shown in ele- 40 vation;

' Fig. 7 is a view similar to Fig. 6 but in which the fuse switch isshown partly open and about to be closed;

Fig. 8v is van oblique section taken on line 8 8 45 of Fig. 7; and,

Fig. 9 is a fragmentary vertical section taken on line 9 9 of Fig. 6. I

Similar reference characters indicate corresponding parts throughout theseveral views A50 of the drawings.

Referring now Imore particularly to Fig. 1, there is shown at numeral Ia box made of insulating material such as porcelain, supported by meansof bolts 3, and having therein conduct- 55 ing line terminals 5. Theline terminals in- Cfr jects will be in part obvious and in part pointedwill be exemplified in the structures hereinafterv (Cl. 20G-114) cludewire clamps 1 for respective line wires (not shown).

Associated with the upper line terminals 5 is a riveted U-shaped springconducting member forming a knife type of contact 9. This contact 5 isof the variety in which the opposite holding faces of Athe springmembers are substantially parallel. To the lower line terminal 5 isriveted a different type of spring conducting member II) (Fig. 10 9).This conducting member I0 is characterized by the fact that the springarms are flared in a downward direction, and also outward. 'Ihe arms areof springlness similar to that of the spring arms forming the knifecontacts 9. The box l has a large opening at the bottom, as indicated atII. The unrestricted character of the opening simplifies the manufactureof the box, besides having other advantages which will beparticularized. The box also has a front opening I3 covered by a door I5hinged on a pin I1. The door I5 is made of insulating material, such asBakelite, for example. Unlike the door of said. application, the presentdoor I5 is hinged at its upper end, the pin I1 being at the 25 upperportion of the box I. 'I'he hooked-shaped portion I9 on the door whichmakes a hinge element is open as shown at 2| so that the door may beremoved from the box after it has been pulled to an open position. Aring 23 is provided for 30 manipulation.

The' door I5 has attached thereto, by means of screws 25, an upper,hollow, terminal-engaging element 21, made of conducting material,having flat sides 3l for engagement with the fiat 35 sides of theU-shaped spring conducting contact 9 of upper line terminal 5.

The spring pressure between the spring arms of contact 9 and theterminal-engaging element 21 is substantial, so that a good contactisobtained under operating conditions without undue temperature rise inthe switch. Y The lower outer corners of the spring arms of contacts 9are flared as shown at 30 to function as guides for the diagonalentrance of the upper 45 terminal-engaging element 21. It will be notedin this connection that element 21 swings around y the center of the pinI1 and therefore enters the. contact 9 diagonally from below. It is forthis reason that the flare is angled. 50 'I'he hollow portion of theupper terminal-engaging element 21 is open at the top and bottom, and atthe top is threaded to receive an enclosing cap 35. The cap alsofunctions as a clamp for the upper headed end 31 of a fuse link 39. 55

The fuse link 39 has a fusible portion 4I adapted to melt upon overloadand to open the circuit. Its lower end is composed of flexibleconducting wire 43. 'A

The fuse link39 passes through a fixed, inner, insulating tube 45 whichis rigidly supported at its upper end by threading to the upperterminal- `engaging element 21. 'Ihe lower end of the tube 45 is open,as indicated at 41.

.Slidably arranged on the insulating tube 45 is a second insulating tubelor sleeve 5I. The lower end of the sleeve 5I is provided with arelatively xed collar 51 which may or may notbe made of conductingmaterial,.althou gh in the present embodiment it is so shown. Thiscollar is formed on one side with a smooth, rounded, anti-frictionsaddle 59 which permits sliding thereov'er of the fuse link wire 43 anddirects it into tube 4s.

The top of the collar 51 forms a seat for a flat bottom 2 which enclosesthe opening II (when the door I5 is closed). The bottom 2 is Y flexiblepart 43 of the fuse link.

The bottom 2 also forms a seat for a spring 6I. Above the spring 6I andslidably arranged upon the outside of the sleeve 5I -is a lowerterminal-engaging element 63,"composed of conducting material. Thiselement or contact 63 is attached by means of screws 6 to an insulatingguide plate B. The screws Ii also extend into and slide in a slot 53arranged in the tube 5I,

Vvsuch that there is a limited relative motion bewhich surrounds astationary pin I4 on the door I5 (Fig. 8). By this means the relativemotion ofthe plate 8 (and consequently also ofthe v,lowerterminal-engaging element B3) and the door I5'is allowed to thesubstantial extent indicated by comparing Figs. 1`and v6.4 Since the 'Yplate 8 is atwise against the door I5,-it prevents rotary movement ofthe tube 5I on the tube 45. v

The lower Aterminal-engagingelement 63 is of special form tomate withthe lower line terminal III, that is, the contact 63 flares downwardlyprimarily (Fig. 8). It also ares somewhat'in the direction of the door.

Aociated with the terminallengaging ele- Ament 63 is a clamp 68 threaded,on a stud 66, by, means of which the lower end 43 ofthe fuse link 39may be bound vto the-terminal-enjgaging element 63.

y Operation of the device is as follows, assuming anew fuse is required:

cap 35 is removed and the old upper fuse portion element removed. Suchlower fuse element V43 as may beheld by the clamp nut 68 The newfusefisfed (flexible part 43 first) of the movable ring 51. It is threadedaround the smooth saddle 59 and then turned upwardly through the slot 4.Its end is 4then fastened by means of the clamp 68. Before fastening ismade, as much as possible of the fuse end 43 is drawn from the tube 45,thus tensioning the fuse 39. Tension may or may not be placed in thespring 6I at this time. In any event the slidable tube 5I (fastened tothe collar 51) is pushed up as high as it will go on the fixed tube 45.

Next, the door I5, while open, has its hook I9 applied under the pin I1(Fig. 7) and is then 'rotated down into closed position (Fig. 1). Thiscauses the `upper fiat-faced terminal-engaging element 21 to befrictionally engaged by the flatfaced spring arms 9.

The lower terminal-engaging element 63 is at this time at such anelevation on door I5 that it is springingly engaged by the spring armsI0 of the lower line terminal. The reaction between the outwardly anddownwardly flowing line arms I0 and the upwardly and inwardly taperedterminal-engaging element 63 causes the latter to be pressed downwardlyagainst the spring 6I to. compressthe latter. This pushes down saddle59v and places tension in the fuse link. It should be understood at thispoint that the bottom 2 moves with the collar 51 and is free of theplate 8, although slidable thereon. The elementv 63 and the plate 9 movedown twice the distance that the fuse link 39, 43 allows collar 51 andtube 5I to move down.

At this time, the reaction between the terminal-engaging element 63 andthe clip I0' causes a. satisfactory low-resistance surface contact whichhas the effect of preventing the building up of switch temperatures.

The surfaces between the terminal-engaging element 63 and clip I0 are soarranged that the component of force exerted downwardly is of a degreeproperly to tension the fuse link. 'I'he direction of this force forcontact reaction is such that the door I5 is not forced 'open againstthe holding 'action of clip 9.

Upon overload, the vfusible fuse portion 4I melts or blows. Thisreleases the saddle 59. and the spring 6I, having theretofore been undercompression, forces the saddle down. This must be, because theterminal-engaging element 63 is held down by clip I0. The saddle 59being part of the collar 51 draws down the attached outer tube 5I,-untilthe upper end of theslot 53 (in tube 5I) strikes the end of the upperone of the\screws 6 (Fig. 5). v

Ihis provides an impact or blow to the lower terminal-engaging element63 to drive it away from engagement with the line terminal I0. It is tobe understood, however, that even without this blow the spring squeezingaction of the lower downwardly flared line terminal I0 would normallysqueeze the terminal-engaging element 63 out and downso that the latterwould be forced out of contact. It will be understood that at this timethere may also be an expulsive action -through the tube 45 due toblowing of the fuse link, depending upon the degree of overload.

As indicated inl Fig. 6, theassembiy of tube` 5I., element E3, Vcollar59, bottom 2, spring 6I and plate '8-slidcs downuntil the pin I4 on thedoor I5 is reached by the end of the slot I2. Support is then by the pinI4, the short telescoped relationship between tubes 45 and 5I at Tfunctioning to steady the assembly. At this time, Vthe lower portionofthe fuse link 43. hangs downwardly. It 'is at this time'electricallydead,

since the terminal-engaging element 63 is separated from its lineterminal l0.

Among the advantages of the invention are those specified in my saidprior application, together with the following:

By eliminating the hinge at the bottom of the door and placing it at thetop of the door, the bottom of the box is left entirely ,clear forclearing parts to drop. Thus it is practicable to employ an enclosingbottom which may drop away as described, without increasing the size ofbox I. Another feature is that more visibility is 0btained by droppingdown more parts for a greater distance. More parts can be dropped awaybecause there is no interference at the bottom opening of the box whenthe hinge is arranged at the top.

Also, better visibility is obtained to indicate blown conditions, andbetter electrical clearance is obtained. At the same time, the circuitopening parts are held captive.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown iii) in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

1. A fuse switch comprising a box, line terminals in the box, said boxhaving an open front and an open bottom, a'door hinged near the upperend of said opening, a fuse supported on the door, terminal-engagingelements on 'the fuse engageable with the line terminals when the dooris closed, one of said terminal-engaging elements being releasab'le fromone of the line terminals when the fuse blows, means movably supportingsaid releasable disengaging element directed to direct the element outof said bottom opening of the box when' the fuse blws, andl meansassociated with the disengageable elementl to close the bottom of thebox during engagement but to open said bottom upon disengagement.

2. A fuse switch comprising a box having a side opening and a bottomopening,.upper and lower line terminals in the box, a door for the boxhinged near the top of said side opening,

a fuse carried by the door having an upper xed terminal-engaging elementfor iixed engagement with the upper line terminal, a lowerterminalengaging element movable on the door, a. fuse link rjoining saidengaging elements and adapted when unseparated to hold the lowerengaging element in position for engagement with the lower line terminalupon closure of the door, said movable engaging element upon blowing ofthe fuse being adapted to move away from the lower line terminal and outoi the bottom of the box.

3. A fuse switch comprising a box having a side opening and a bottomopening, upper and lower line terminals in the box, a door vfor the boxhinged near the top of saidy side opening, a fuse carried by the doorhaving an upper ilxed terminal-engaging element for fixed engagementwith the upper line terminal, a lower terminalengaging element movableon the door, a fuse link joining said engaging elements and adapted whenunseparated to hold the lower engaging element in position forengagement with the lower line terminal upon closure of the door, saidmovable engaging element upon blowing of the fuse being adapted to moveaway from the lower line terminal and out of the bottom of the box, anda bottom carried with said movable engaging element adapted to close thebottom opening when the movable engaging element is engaged and viceversa.

4. A fuse switch comprising a box having a side vopening and a bottomopening, line terminals in the box, a door for the box hinged near thetop of said side opening, a fuse carried by the door having an upper xedterminal-engaging element for engagement with the upper line terminal inthe box, a lower terminal-engaging element movable with respect to thedoor, a fuse link joining said engaging elements and adapted whenunblown to hold the lower engaging element for engagement upon closureof the door, said movable engaging element upon separation of the fuselink beingl adapted to move away from the lower line terminal and out ofthe opening at the bottom of the box, a bottom for the box carried bysaid movable engaging element and adapte ed to be positioned to closesaid bottom opening 'when the movable engaging element is engaged and tomove away from said opening upon disengagement of the movable engagingelement.

l THEODORE BIRKENMAIER.

